METHOD FOR PRODUCING LOW-MOLECULAR WEIGHT BLOCK COPOLYMER OF ETHYLENE AND VINYL ACETATE (VERSIONS) Russian patent published in 2023 - IPC C08F210/02 C08F218/08 

FIELD: polymers.

SUBSTANCE: method for obtaining an ethylene-vinyl acetate copolymer. Two variants of a method for obtaining a low molecular weight block copolymer of ethylene and vinyl acetate by radical copolymerization in a medium of two solvents - dimethyl carbonate and tetrahydrofuran and a radical copolymerization initiator - dicumyl peroxide, which is preliminarily dissolved in a mixture of dimethyl carbonate and tetrahydrofuran in a container evacuated and filled with argon, are described, the reaction of radical copolymerization is carried out in a reactor, pre-evacuated and filled with ethylene, where, according to the first variant, a pre-obtained solution of dicumyl peroxide in a mixture of DMC dimethyl carbonate and tetrahydrofuran THF is loaded, and then vinyl acetate in the following volumetric ratio of components: V(vinyl acetate):V(THF):V(DMC) = 0.19-0.74:0.33-1.81:3.97-5.57 and the molar ratio of vinyl acetate:dicumyl peroxide is 203:1-222:1, then the temperature in the reactor is raised to the decomposition temperature dicumyl peroxide, and the pressure is up to 7-10 MPa, maintained under the indicated conditions for at least 2 hours until the completion of the copolymerization reaction, then the reactor is cooled to room temperature, the pressure is released to atmospheric pressure, the resulting liquid reaction product is unloaded, light-boiling components are removed - unreacted vinyl acetate, dimethyl carbonate and THF on a rotary vacuum evaporator at a temperature of 70°C and pressure up to 6 mm Hg to obtain the finished product - a copolymer of ethylene and vinyl acetate with a molecular weight of 2.0⋅10³-6.7⋅10³. According to the second option, the previously obtained solution of dicumyl peroxide in a mixture of dimethyl carbonate DMC and tetrahydrofuran THF is divided into two equal portions, the radical copolymerization reaction is carried out in the reactor as in the first option, but initially the first portion of the obtained solution of dicumyl peroxide in a mixture of dimethyl carbonate DMC and tetrahydrofuran THF is loaded, and then vinyl acetate at a volume ratio of components: V(vinyl acetate):V(THF):V(DMC) = 0.19-0.74: 0.33-1.81: 3.97-5.57 and the molar ratio of vinyl acetate: dicumyl peroxide is 103:1-203:1, then the temperature in the reactor is raised to the decomposition temperature dicumyl peroxide, and the pressure is up to 7-10 MPa, is kept under the indicated conditions for at least 2 hours, then the second portion of the indicated dicumyl peroxide solution is loaded, again kept under the same conditions for at least 2 hours, then the process is carried out as in the first variant.

EFFECT: increase in the specific yield of the copolymer up to 69 wt.%; the ability to control the molecular weight of the resulting copolymer and the molar fraction of vinyl acetate in the copolymer within 5.6-14.6 mol.% with safety, environmental friendliness and simplicity of the method for obtaining, without the use of highly toxic reagents.

3 cl, 1 dwg, 10 ex